Fuel injection control system



Aug. 26, 1969 w. REICHARDT ETAL FUEL INJECTION CONTROL SYSTEM Filed Oct. 24, 1967 /NVENTOP5 fleferi/c/a 5 b a/fgcng Paw/4917f #ermann SEA/OIL 055 ital L United States Patent 3,463,130 FUEL INJECTION CONTROL SYSTEM Wolfgang Reichardt, Stuttgart-Ruhr, Dieter Eichler, Bonlanden, Hermann Scholl, Stuttgart, and Josef Wah],

Stuttgart-Kaltental, Germany, assignors to Robert Bosch G.m.b.H., Stuttgart, Germany, a limited-liability company of Germany Filed Oct. 24, 1967, Ser. No. 677,566 Claims priority, application6ggermany, Nov. 3, 1966,

Int. (:1. F021) 3/512,- F02d 31/00 US. Cl. 123-32 8 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a fuel injection system for internal combustion engines and more particularly to a control system to control electromagnetically operated injection valves in dependence on operating parameters of the internal combustion engine.

Fuel injection systems for internal combustion engines have the advantage that good combustion of the fuel can be obtained and thus the energy of the fuel can be utilized efiiciently. Further, the proportion of noxious gases in the exhaust, such as carbon monoxide, can be reduced. The content of noxious gases is particularly increased when the internal combustion engine need not produce power, for example, when it is idling, during braking of the vehicle, or during coasting, for example, downhill. Additionally, if the engine is not required to deliver power, fuel supplied thereto in excess of its idling requirements is wasted, thus decreasing the economy of operation of the engine.

It is an object of the present invention to provide a fuel injection control system for internal combustion engines in which the exhaust from the engine has a minimum of noxious contents, even during coasting or braking of the vehicle, and in which the overall fuel economy is improved.

Subject matter of the present invention Briefly, in accordance with the present invention, an electronic circuit supplies impulses to electromagnetically operated fuel injection valves, timed in dependence on the speed of the engine. The length of the impulses depends on operating parameters of the engine and is controlled by a sensing device sensing the vacuum in the intake manifold, as determined by the throttle position controlling the engine.

A blocking circuit is provided to disable application of fuel injection impulses by the electronic circuit to the fuel injection valves upon the occurrence of conditions when no fuel should be supplied. To this end, the blocking circuit is interconnected with the engine controller, that is, the gas pedal, and is further responsive to the speed of the engine, so that, when the engine speed is in excess of a certain predetermined value and the engine controller is set so that the throttle is closed, or almost closed, the blocking circuit will prevent application of fuel injection impulses to the fuel injection valves.

3,463,130 Patented Aug. 26, 1969 The operation of the blocking circuit can be readily controlled. In accordance with a feature of the invention, the blocking circuit is disabled at low temperatures in order to prevent stalling of the engine when it is still cold.

The structure, organization, and operation of the invention will now be described more specifically with reference to the accompanying drawing which illustrates a circuit in accordance with the invention, partly in schematic form.

The drawing illustrates a four cylinder internal combustion engine 10, having spark plugs 11, connected to a high tension source not illustrated. Electromagnetically operated injection valves 13 are located in the individual cylinder branches connected to an intake manifold 12 and located in immediate vicinity of the inlet valves (not shown) of the internal combustion engine 10. The four injection valves 13 together form fuel injection means for the internal combustion engine 10. Fuel is supplied to each valve 13 under constant pressure from a fuel supply over lines 14.

The coils 13 of the fuel injection valves 13 are combined in two groups which are alternately operated. As shown, the two left valves are the two right valves (referring to the figure) each form one group. For operation, two windings 13' are respectively connected over resistances 15 to the collector of an npn power transistor 16, 17, respectively. When transistor 16 or 17, respectively, is conductive then the valves 13 connected thereto are opened so that the fuel is injected to the respective cylinders, the amount being proportional to the opening time of the valves 13.

The opening time of valves 13 depends on the operating parameters of the engine 10. A monostable multivibrator 18 provides pulses in synchronism with the speed of the engine, as determined by the closing of a switch 20, operated by a double-rise cam 21, and driven from the engine camshaft as indicated by the broken line in schematic form. The contacts of switch 20 will thus close twice during each rotation of the camshaft of the engine and serve as a pulse source.

The multivibrator 18 serves as an electronic control device and contains a timing circuit such as a R-C, or a L-R circuit which determines the impulse duration of the multi vibrator. A vacuum chamber 22, connected to the intake manifold 12, controls the timing constant of this timing circuit in such a manner that, when a throttle 23 is closed, the impulse period and thus the injection period of fuel is decreased. Thus, as the vacuum in intake manifold 12 increases, less fuel is injected. When the throttle 23 is opened, the impulse period is increased and more fuel is injected.

The output pulses of the multivibrator 18 are connected over a transfer switch 24 to a pair of AND gates 25, 26 each containing a transistor 27, 28. The transfer switch 24 is likewise controlled from the camshaft of the engine 10.

The emitters of the transistors 27, 28 are connected to the chassis and thereover with the negative terminal of a source of DC potential, for example, an automotive battery of 12. volts. The emitter of the output transistors 16, 17 are connected together and to the anode of a rectifier 29, the cathode of which is likewise connected to the chassis. This rectifier provides the bias for the bases of transistors 16 and 17.

The collector of the transistor 27 is directly connected with the base of a transistor 16 and further over a resistance 32 to a positive polarity bus 33, connected to the positive terminal of the battery. The collector of transistor 28 is similarly connected with the base of the transistor 17 and over a resistance 34 again to the positive bus 33. The collectors of transistors 16 and 17 are connected over a pair of parallel connected series circuits comprising a resistance and the winding 13' of the injection valves 13 to the positive bus 33.

The base of the transistor 27 is connected over a resistance 35 to the upper fixed contact of the transfer switch 24 and over a resistance 36 to the output of a bistable multivibrator 38. The base of transistor 28 is likewise connected over a resistance 41 to the multivibrator 38. The base of transistor 28 is further connected over a resistance 42 with the lower fixed contact of transfer switch 24. A movable contact of transfer switch 24 is connected to the output of the multivibrator 18.

The input of multivibrator 18 is connected over resistance 43 with the positive bus 33. Further, the input of multivibrator 18 is connected to one terminal of the interruptor switch 20, the other terminal of which is connected with the chassis or ground.

Let it be assumed that the output of the bistable multivibrator 38, to which the resistance 36 and 41 are connected, is at chassis potential. Under these conditions, the multivibrator 38 permits operation of the injection system. If a negative impulse is obtained from multivibrator 18, conducted over transfer switch 24 to transistor 27, then this previously conductive transistor is blocked. Its collector becomes more positive, and power transistor 16 becomes conductive so that fuel for the two left cylinders of the motor 10 can be injected. 1f the transfer switch 24, at the next pulse, is in its lower position, then the right transistor 28 is blocked, power transistor 17 becomes conductive so that during the impulse period fuel is injected for the two right cylinders of motor 10.

The multivibrator 38, serving as a blocking circuit includes two npn transistors 45, 46, having their emitters directly connected to the chassis. The base of transistor 45 is connected over a resistance 47 to the chassis. A resistance 48 further connects the base of transistor 45 to the collector of a transistor 46, which serves as the output for the multivibrator 38, and to which the resistances 36, 41 are connected. The collector of transistor 46 is further connected over a collector resistance 49 to the positive bus 33.

The base of transistor 45 is connected further with the anode of a diode 52, the cathode of which connects to a junction 53. Junction 53 connects to the cathode of a diode 54, one electrode of a condenser 55, and to a resistance 56 connected at its other end to chassis. The cathode of a diode 57 and the anode of the diode 54 are interconnected, and both in turn connect to a condenser 59, the other terminal of which is connected to the input to multivibrator 18 and hence to one terminal of interruptor contact 20. The anode of diode 57 and the other electrode of condenser 55 connect over a resistance 58 to chassis. The elements 52 to 59 together form a first passive network.

The input to multivibrator 18, and hence one contact of interruptor switch 20, further has a resistance 62 connected thereto, the other terminal of which is connected with one electrode of a condenser 63, the cathode of a diode 64 and series-connected resistances, 65, 66, which connect back to the anode of diode 64. A condenser 67 connects the anode of diode 64 to the chassis. Further, a resistance 68 connects the anode of diode 64 to the other electrode of condenser 63 and to the cathode of a diode 69. The circuit elements 62. to 68 together form a second passive network.

The anode of diode 69 connects to a junction 76 and to the base of transistor 46. The base is further connected over resistance 78 to the chassis. The collector of transistor 45 is connected over a collector resistance 83 with the positive bus 33 and over a resistance 84 with junction 76. The cathode of a diode 70 further connects to the junction 76.

The anode of cathode 70 is connected over a resistance 88 to the positive bus 33, and further, to a bi-metallic switch 85 which is connected in heat conductive relationship to the motor 10 and closes only when the motor has reached operating temperature. Switch 85 thus serves as a circuit element dependent on the temperature of the engine 10.

A switch 86, the open or closed position of which depends on the position of the fuel control, or gas pedal 87, connects bimetallic switch 85 to the chassis. Switch 86 is only closed when the throttle 23 is closed, or almost closed. The drawing illustrates an operative connection between the gas pedal and the switch 86, which gas pedal of course controls the throttle 23 through linkages not shown in the drawing. Thus, switch 86 will be closed only when the fuel control commands operation of the motor in or near idling.

The bistable multivibrator and the cooperating circuit components operate as follows: If one of the switches 86 or 85 are open, diode 70 will be conductive. Current can flow to the base of transistor 46 which is kept conductive. The collector of transistor 46, to which the resistances 36 and 41 are connected, is thus at the chassis potential and the injection control system operates, as above described, since the AND circuits 25, 26 pass the impulses coming from multivibrator 18.

If both switches 85 and 86 are closed, the anode of diode 70 is connected to chassis potential and this diode blocks. The switching condition of the bistable multivibrator 38 thus depends on the frequency of the impulses which are applied from the pulse switch 20, and thus depends on the speed of the engine 10. The first passive network, consisting of elements 52 to 59 is so dimensioned that below a lower limit of, for example, 1,100 r.p.m., negative impulses are passed to the base of transistor 45, thus blocking this transistor and causing conduction of transistor 46 over resistance 84. The injection system thus operates normally and as above described.

The second passive network, consisting of circuit components 62 to 68, passes negative impulses above an upper speed limit, for example, 1,800 r.p.m., to the base of transistor 46, thus blocking this transistor and controlling transistor 45, over resistance 48, to be conductive. The collector of transistor 46 will be at the potential of the positive bus 33 so that over resistance 36 current will be applied to the base of transistor 27 and, over resistance 41, current will be applied to the base of transistor 28. Transistors 27 and 28 thus both become conductive, block transistors 16 and 17, and thus block application of current to the coils 13 of the injection valves 13.

The operating parameters of the engine therefore have these effects: when the temperature of the engine 10 is too low, switch 85 permits injection of fuel regardless of speed. When the engine 10 reaches its operating temperature, injection of fuel is enabled after the throttle 23 has passed a certain minimum opening, that is, has reached a position at which switch 86 is open.

When the engine 10 has reached its operating temperature and the throttle 23 is, however, almost or entirely closed, then above an upper speed of 1,800 r.p.m. (in the above example) injection of fuel will be blocked; it will be enabled again when the speed drops to a certain lower limit, for example, 1,100 r.p.m. This prevents incomplete combustion of fuel during coasting or braking of a vehicle, causing fumes from the exhaust and polluting ambient air; further, fuel is saved. However, fuel is injected when the speed of the engine drops below a certain value to prevent stalling.

The speeds above referred to at which fuel is supplied and cut off are, of course, illustrative and depend on the design of the particular engine.

Diode 69 and diode 70, connected to junction 76, together form an AND gate generally indicated at 71 to block transistor 46 upon concurrence of the following conditions: speed above 1,800 r.p.m. and temperature above minimum and throttle closed.

We claim:

1. Fuel injection control system for internal combustion engines having a throttle (23);

operator settable control means (87) connected to said throttle;

fuel injection means for said engine;

means (22) sensing an operating parameter of said engine;

means (20, 21) sensing the speed of said engine;

electrical circuit means (18, 25, 26) connected to said operating parameter sensing means (22) and to said speed sensing (20, 21) means and having an output (16, 17) supplying pulses to said fuel injection means (13) to operate said fuel injection means and inject fuel for operation of said engine, the pulse duration depending on an operating parameter of said engine, and the pulse repetition rate depending on the speed of said engine;

means (86) sensing almost closed, or closed position of said settable control means; and

a blocking circuit (38), said blocking circuit having its input connected to said settable control means position sensing means (86) and to said engine speed sensing means (20, 21) and having its output (46) connected to said electric circuit means, said blocking circuit having means (69, 70) sensing the logical conjunction of (a) closed or almost closed throttle position, and (b) engine speed in excess of a predetermined value, said blocking circuit inhibiting supply of pulses from said electrical circuit means to said fuel injection means upon said sensed logical conjunction.

2. System as claimed in claim 1 including a temperature-sensitive switching element dependent on the temperature of the engine and connected to said blocking circuit and controlling the state thereof; to disable said blocking circuit at temperature levels below a predetermined value.

3. System as claimed in claim 1, wherein said means sensing closed, or almost closed position of said operator settable control means (87) comprises a switch (86) arranged to change state when the operator settable control means just reaches a position corresponding to closed throttle, said switch controlling the state of said blocking circuit (38).

4. System as claimed in claim 3, including a temperature sensitive switch dependent on the temperature of the engine and connected to control the state of said blocking circuit, said temperature sensitive switch being connected in circuit with said engine controller switch (86) and overriding blocking action of said blocking circuit at temperatures below a predetermined value regardless of the position of the operator settable control means.

5. System as claimed in claim 1, wherein said blocking circuit (38) includes a double input multivibrator circuit, said circuit having a blocking state and an unblocked state; said engine speed sensing means includes a pulse source (20) supplying speed pulses in synchronism with engine speed; a first passive network (52-59) having said speed pulses applied thereto is connected to one input of said multivibrator circuit to control said multivibrator circuit to switch to unblocked state when the speed of the engine is below a predetermined value; a second passive network (62, 68) having said speed pulses applied thereto is provided; a switching element controlled by the position of said engine controller; and means interconnecting said second passive network (62- 68) and said switching element (86) and connected to the other input of said multivibrator circuit to control said multivibrator to switch into blocked state when (a) said switching element is in a position corresponding to closed, or almost closed state of the throttle of the engine as determined by said operator settable control means (87) and (b) the engine speed is in excess of said predetermined value.

6. System as claimed in claim 5, including a temperature sensitive switching element dependent on the temperature of the engine and in circuit with the second input to said multivibrator circuit, said temperature sensitive switching element being connected to enable said multivibrator circuit only if the temperature is above a predetermined value.

7. System as claimed in claim 5 wherein said lower pre-determined value is less than said upper predetermined value.

8. System as claimed in claim 1, wherein said electrical circuit means supplying pulses to said valves (13) includes an AND gate (25-, 26); and an electronic control circuit (18, 24) to control application of injection pulses to said valves is provided; one input of said AND gates being connected to said electronic control circuit and the other input of said AND gates being connected to said blocking circuit (38).

References Cited UNITED STATES PATENTS 2,948,272 8/1960 Woodward et al. 123119 3,005,447 10/1961 Baumann et al. 123119 3,032,025 5/1962 Long et al.

LAURENCE M. GOODRIDGE, Primary Examiner U.S. Cl. X.R. 

